Some hydrocarbon production fields have boreholes which penetrate to various different depths, so that production from two or more different levels or geological formations may simultaneously occur. Some of these wells may be dual completed, whereupon production from two different zones are maintained separated from one another but are produced concurrently from the same wellbore. In this same oil field, there may be other boreholes which extend to only one of the multiple production levels.
Sometimes difficulties are experienced with dual completion wells. For example, in the case of a dual completed well having an extremely high pressure lower formation, the lower packer has been known to fail, whereupon high pressure hydrocarbons from the lower payzone rush uphole and commence entering the upper payzone. This sudden release of high pressure hydrocarbons can shock the upper packer with sufficient force to cause the packer to fail. The upper packer loses control of the well, and under extreme conditions erosion of the upper perforated zone commences cavitating the formations.
The above failure may continue to progress until it is impossible to shut-in the well using conventional methods. Drilling mud cannot be pumped down the borehole in order to kill the well because of the damaged area surrounding the upper formation. Until the well is killed, valuable hydrocarbons from the lower zone are lost into the upper zone.
Many high pressure wells extend through thousands of feet of salt formation. It is possible for the salt formation to shift laterally with sufficient shear force to sever the casing and production tubing, whereupon the high pressure fluid is uncontrollably released into the salt formation.
Earthquakes and other disturbances brought about by abnormal geological phenomena can have similar devastating effects and cause below surface blowout of oil wells.
Method and apparatus by which a subsurface well blowout, such as described above, can be brought under control is the subject of the present invention.